Cable television (CATV) is a form of broadcasting that transmits programs to paying subscribers via a physical land based infrastructure of coaxial (“coax”) cables or via a combination of fiber-optic and coaxial cables (HFC).
CATV networks provide a direct link from a transmission center, such as a head-end, to a plurality of subscribers at various remote locations, such as homes and businesses, which are usually stationary and uniquely addressable. The head-end may be connected to the subscribers via local hubs, commonly referred to as “nodes”, which route the flow of data to and/or from a predefined group of subscribers, e.g., hundreds of subscribers, in a defined geographical area, for example, a small neighborhood or an apartment complex.
Existing CATV networks utilize a signal distribution service to communicate over multiple channels using various formats, for example, analog and/or digital formats for multi-channel TV programs, a high definition TV (HDTV) format, providing interactive services such as “video on demand”, and other multimedia services, such as Internet access, telephony and more.
In a conventional HFC cable TV system, the head-end receives data from a wide-area data communication network, e.g., the Internet, via a Cable Modem Termination System (CMTS) interface. The head-end is connected to the local nodes via a fiber portion (“trunk”), which includes optic cables for transmitting optical signals between the head-end and the local node.
Downstream signals, which are limited to designated channels within a standard (“legacy”) downstream frequency range (band) of 48 MHz to 860 MHz (or up to 1,000 MHz by recently introduced Stretching technology), are modulated by the head-end on a light beam, e.g., at a standard wavelength of about 1550 nm, and sent to the local node via the fiber trunk. An optical converter at the local node detects the optical signals and converts them into corresponding electrical signals, which may be modulated over a radio frequency (RF) carrier, to be routed to the subscribers via a coaxial (“coax”) trunk. The coax trunk includes distribution cables, drop cables, amplifiers and splitters.
In the reverse direction (the upstream direction), the local optical node receives upstream data from the local subscribers via the coax trunk. These are carried by RF electrical signals at a standard upstream frequency band of 5 MHz to 42 MHz, which does not overlap with the downstream frequency band. A converter in the local optical node converts the upstream data into corresponding optical signals by modulating the data on an optical carrier beam, e.g., at a wavelength of about 1310 nm, to be transmitted back to the head-end.
The currently utilized legacy frequency band of between about 5 MHz and about 860 MHz limits the number of available downstream and upstream channels. In many applications the frequency band of 542 MHz is used for upstream transmission, and the frequency band of 50-860 MHz is used for downstream transmission.
Some Multi-system Operators (MSOs) implement the Data Over Cable Services Interface Specification (DOCSIS) protocol for Internet access, e.g., for Small and Medium Businesses (SMBs). The SMBs typically require relatively high data throughput in both the upstream and downstream directions. The currently utilized legacy frequency band may not be sufficient for providing the upstream and/or downstream throughputs required by the SMBs.